Field of the Invention
This invention relates to a reflector antenna. More particularly, the invention provides a low-cost, self-supported sub-reflector assembly configured to provide a reflector antenna with a low side-lobe signal radiation pattern characteristic.
Description of the Related Art
This section introduces aspects that may help facilitate a better understanding of the invention. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is prior art or what is not prior art.
An example of a dielectric cone feed sub-reflector configured for use with a deep-dish reflector is disclosed in commonly owned U.S. Pat. No. 6,919,855 (“the '855 patent”), the teachings of which are incorporated herein by reference in their entirety. The '855 patent utilizes a dielectric block cone feed with a sub-reflector surface and a leading cone surface having a plurality of downward angled non-periodic perturbations concentric about a longitudinal axis of the dielectric block. The cone feed and sub-reflector diameters are minimized where possible, to prevent blockage of the signal path from the reflector dish to free space. Although a significant improvement over prior designs, such configurations have signal patterns in which the sub-reflector edge and distal edge of the feed boom radiate a portion of the signal broadly across the reflector dish surface, including areas proximate the reflector dish periphery and/or a shadow area of the sub-reflector where secondary reflections with the feed boom and/or sub-reflector may be generated, degrading electrical performance.
Dielectric block-type sub-reflector supports with dielectric radiator structures are also known. Laterally projecting dielectric radiator structures separate from sub-reflector support portions of the dielectric block have been shown to enhance signal patterns by drawing the energy field distribution away from the waveguide supporting the dielectric block. This form of dielectric block sub-reflector has previously been applied to deep-dish-type main reflectors, for example with a focal length (F) to diameter (D) ratio of 0.25 or less.